1. Field of the Invention
The present invention relates to an image deviation correcting optical apparatus to drive a corrective optical system for correcting the optical axis deviation of a lens barrel when a picture is taken by a hand-held camera.
2. Related Background Art
There has already been proposed a corrective optical system in which a part of an optical system (or the entirety thereof as a matter of course) in an optical apparatus is structured as a corrective optical system in order to correct image deviation (blurred image by shake) due to unsteady motions given to the optical apparatus.
For example, in Japanese Patent Laid-Open Application No. 2-120821, an image deviation correction apparatus is disclosed. This apparatus comprises a deviation detector and a deviation correcting optical system, and the aforesaid deviation detector is structured to serve also as a detector for detecting the working amount of the corrective optical system.
Also, an optical supporting mechanism for a corrective optical system (Japanese Patent Laid-Open Application No. 2-162320) is known as an apparatus of the kind, in which there are provided a plurality of substantially rigid long beams supported by a fixed body. The beams are extended in the direction of the optical axis and at the same time, are allowed to rotate around the directions of two axes perpendicular to the optical axis and intersecting at right angles to each other, respectively, but not allowed to rotate around the optical axis. Optical systems are connectively supported at the respective oscillating ends of these beam members through the joints which are slantedly movable.
Although the above-mentioned correction apparatuses conventionally known are applicable to an ideally thinned single lens, there is an unavoidable problem space-wise that when they are applied to an exchangeable lens for an interchangeable lens camera, it is difficult to mount a deviation detector which dually functions to detect the working amount of the corrective optical system because of the existing thickness of the body side.
Further, there is a drawback from the standpoint of the space availability for the mounting of the deviation detector to be adopted for the lens groups of complex structures often employed for a still camera and the like, such as proposed by the assignee hereof in Japanese Patent Laid-Open Application No. 2-234115 wherein a rear lens group is driven for the required deviation correction.
Also, in the conventional apparatuses described above, the constituents of the deviation detector are divided to be members which form the housing for the optical apparatus and those which construct the corrective optical system. As a result, there is encountered a problem that it takes a considerable time to mount them and make the necessary adjustment therefore. It is therefore desired that an effective measure should be taken to solve this problem too.
Particularly, in the above-mentioned conventional example disclosed in the Japanese Patent Laid-Open Application No. 2-120821, the distance from the corrective optical system (that is, a focusing lens which can be shifted) to the reflective mirror of the hydrostatic sensor must be more than half of the distance to the film plane according to an embodiment shown in FIG. 9 thereof.
In other words, given a deviation angle as .theta. and a lens focal length as f, an image deviation amount D=f.times..theta. (in a case of an object in a long distance, the description will be made on this assumption in the present specification). Then, a driving amount D' of the corrective optical system required to correct the image deviation amount in this case is D'=D. Therefore, given the distance between the corrective optical system (a focusing lens which can be shifted) and the reflective mirror of the hydrostatic sensor as A, it is necessary to satisfy a condition of 2.times.A.times..theta.=f.times..theta., 2.times.A=f.
Notwithstanding, this condition is too severe for a conventional structure to satisfy because in the case of the exchangeable lens, the space behind its mounting position cannot suitably be utilized.
Also, in an apparatus having the structure of an optical system for a vibration proof telephotographic lens disclosed in the above-mentioned Japanese Patent Laid-Open Application No. 2-234115, the usual condition is D.apprxeq.D' in order to maintain its optical performance. Nevertheless, it is necessary to make the distance A from the corrective optical system to the film plane to be A&lt;&lt;f. Therefore, even if the lens systems are integrally provided with the body, it is impossible to secure the distance A. Most of the usual lenses for a camera are of such a structure as this, and if D'&lt;D, A can be made small, but to deviate from "=" results in creating many difficult problems with respect to the optical performance, and this should be taken into account.
In the aforesaid conventional structure, the beam members are caused to oscillate rotatively around the axes respectively in the two-axis directions perpendicular to the optical axis and intersecting at right angles with each other. The oscillation in the direction of the optical axis of the corrective optical system (cosine error) is generated by the structural driving. Accordingly, the focal position is deviated in the direction of the optical axis.
Also, in order to minimize the aforesaid cosine error, a comparatively heavy corrective optical system should be arranged at a position which is comparatively far away from the rotational shaft of the supporting mechanism. As a result, the moment created by its dead weight becomes great, and the weight (balancing member) to keep the supporting mechanism balanced becomes unavoidably heavy. Thus the reaction due to the driving tends to be great, and there is a danger that the image deviation created by unsteady hands and the like is intensified depending on the direction in which the reaction is generated.
In addition, the corrective optical system is supported by the long beam members and the slantedly movable joints are used for connecting the supporting member and corrective optical system. There tends to occur self-sustained vibration due to deflection or the like in driving the mechanism. Hence a problem of strength is encountered.